This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The focus of this project is to explore how muscles grow. Muscle wasting is a common phenomenon in many conditions, such as cancer, AIDS, trauma, sepsis, kidney failure, and is also particularly prevalent in the elderly. Specific aims are to: (1) determine the magnitude of the short-term response of muscle growth to feeding when the food is given before or after a bout of resistance exercise. (2) determine the magnitude of the short-term response of muscle growth to food that provides an amount of energy that either matches or exceeds the amount of energy used during the exercise. (3) determine the differences between women and men in the short-term response of muscle growth to weight lifting alone and in combination with feeding when ingested before or after a bout of weight lifting exercise. The procedures include the use of femoral catheters, weight lifting exercise, blood and breath collection and taking muscle biopsies. During each experiment we will be continuously infusing stable isotopes. Stable isotopes are not radioactive and can be given safely to humans. These stable isotopes allow us to be able to measure short-term muscle growth in humans. These studies will provide insight into the mechanisms that regulate human muscle growth, and will be utilized as a basis from which to develop interventions for improving muscle growth in conditions such as aging, trauma, cancer, and AIDS.